Method of fabricating a field emmision cold cathode

Abstract

There is provided a method of fabricating a field emission cold cathode, including the steps, in sequence, of (a) forming a first insulating layer on a substrate and further forming a first electrode layer on first insulating layer, (b) forming at least one opening in first electrode layer, (c) forming a second insulating layer on first electrode layer and further forming a second electrode layer on second insulating layer, (d) forming at least one opening in second electrode layer, (e) optionally repeating steps (c) and (d) predetermined number of times, (f) forming a cavity extending from an uppermost electrode layer to substrate, (g) forming a first sacrifice layer around a first opening of a first electrode layer, (h) forming a second sacrifice layer around a second opening of a second electrode layer, and (i) forming an emitter electrode on substrate with first sacrifice layer being used as a mask. The method enables a field emission cold cathode including a focusing electrode to have small misalignment between an opening of a first opening of a first electrode layer and an emitter electrode to the same degree as that of a field emission cold cathode including no focusing electrode.

What is claimed is: 
     
       1. A method of fabricating a field emission cold cathode, comprising the steps, in sequence, of: (a) forming a first insulating layer on a substrate and further forming a first electrode layer on said first insulating layer;   (b) forming at least one opening in said first electrode layer;   (c) forming a second insulating layer on said first electrode layer and further forming a second electrode layer on said second insulating layer;   (d) forming at least one opening in said second electrode layer;   (e) forming a cavity extending from an uppermost electrode layer to said substrate; and   (f) forming a first sacrifice layer on said second electrode layer surrounding said at least one opening in the second electrode layer and on an exposed portion of the first electrode layer;   (g) forming an emitter electrode on said substrate in said first insulating and electrode layers.   
     
     
       2. The method as set forth in claim 1, wherein said cavity is formed in said step (c) by etching said insulating layers with said electrode layers lying on said insulating layers being used as masks. 
     
     
       3. The method as set forth in claim 1, wherein an opening formed in an electrode layer has a larger area than an area of an opening formed in electrode layers located therebelow. 
     
     
       4. A method of fabricating a field emission cold cathode comprising the steps, in sequence, of: (a) forming a first insulating layer on a substrate and further forming a first electrode layer on said first insulating layer;   (b) forming at least one opening in said first electrode layer;   (c) forming a second insulating layer on said first electrode layer and further forming a second electrode layer on said second insulating layer;   (d) forming at least one opening in said second electrode layer;   (e) forming a cavity extending from an uppermost electrode layer to said substrate;   (f) forming a first sacrifice layer around an opening of said electrode layer including on an exposed portion of said first electrode layer; and   (g) forming an emitter electrode on said substrate with said first sacrifice layer formed on said first electrode layer being used as a mask.   
     
     
       5. The method as set forth in claim 4, wherein said first sacrifice layer is formed around an opening of said first electrode layer. 
     
     
       6. The method as set forth in claim 5, wherein said first sacrifice layer is formed in said step (f) by oblique evaporation of source material, said source material being deposited around said opening with an incident angle defined so that evaporation of source material is not interrupted by edges of an opening formed in an uppermost layer and source material deposits on an electrode layer which will act as a mask when an emitter is formed on said substrate. 
     
     
       7. The method as set forth in claim 4, wherein said cavity is formed in said step (c), at least in part, by etching said electrode layers with reactive ion etching (RIE) and by etching said insulating layers with buffered hydrofluoric acid (BHF). 
     
     
       8. A method of fabricating a field emission cold cathode, comprising the steps, in sequence, of: (a) forming a first insulating layer on a substrate and further forming a first electrode layer on said first insulating layer;   (b) forming at least one first opening in said first electrode layer;   (c) forming a second insulating layer on said first electrode layer and further forming a second electrode layer of said second insulating layer;   (d) forming at least one second opening in said second electrode layer;   (e) forming a cavity extending from an uppermost electrode layer to said substrate;   (f) forming a first sacrifice layer around a first opening of the first electrode layer;   (g) forming a second sacrifice layer around a second opening of the second electrode layer; and   (h) forming an emitter electrode on said substrate with said second sacrifice layer being used as a mask.   
     
     
       9. The method as set forth in claim 8, wherein said first sacrifice layer is formed on an uppermost electrode layer. 
     
     
       10. The method as set forth in claim 8, wherein said first sacrifice layer is formed by oblique evaporation of source material, said source material being deposited with a first incident angle defined so that obliquely evaporated source material covers therewith an inner sidewall of an opening formed in said uppermost electrode layer. 
     
     
       11. The method as set forth in claim 8, wherein said second sacrifice layer is formed by oblique evaporation of source material, said source material being deposited with a second incident angle defined so that evaporation of source material is not interrupted by edges of an opening formed in an uppermost layer and source material deposits on an inner sidewall of an opening formed in an electrode layer located below said uppermost layer. 
     
     
       12. The method as set forth in claim 8, wherein the second sacrifice layer has a greater density than a density of said first sacrifice layer. 
     
     
       13. The method as set forth in claim 8, wherein said second sacrifice layer is formed by oblique evaporation of source material, said source material being deposited with a second incident angle defined so that said second sacrifice layer covers said first sacrifice layer therewith. 
     
     
       14. The method as set forth in claim 8, wherein said first sacrifice layer is further formed in said step (f) on an upper most layer, and further wherein the step of forming the second sacrifice layer comprises forming the second sacrifice layer on said first sacrifice layer. 
     
     
       15. The method as set forth in claim 8, wherein said first and second sacrifices layers are formed with different incident angles in oblique evaporation of source material. 
     
     
       16. The method as set forth in claim 8, wherein said first and second sacrifices layers are formed with incident angles for oblique evaporation of source material being continuously varied. 
     
     
       17. The method as set forth in claim 8, wherein said incident angle is increasing from a first incident angle for forming said first sacrifice layer to a second incident angle for forming said second sacrifice layer. 
     
     
       18. The method as set forth in claim 8, wherein said incident angle is decreasing from a first incident angle for forming said first sacrifice layer to a second incident angle for forming said second sacrifice layer. 
     
     
       19. The method as set forth in claim 8, wherein said incident angle is varied reciprocatingly between first and second predetermined angles. 
     
     
       20. The method as set forth in claim 8, wherein said first and second sacrifices layers are formed with incident angles in oblique evaporation of source material being varied in stages. 
     
     
       21. The method as set forth in claim 8, wherein said second sacrifice layer has a portion formed by oblique evaporation of source material with an incident angle of 70 degrees or greater with respect to an axis perpendicular to said substrate. 
     
     
       22. A method of fabricating a field emission cold cathode, comprising the steps, in sequence, of: (a) forming a first insulating layer on a substrate and further forming first electrode layer on said first insulating layer;   (b) forming at least one first opening in said first electrode layer;   (c) forming a second insulating layer on said first electrode layer and further forming a second electrode layer on said second insulating layer;   (d) forming at least one second opening in said second electrode layer;   (e) forming a cavity extending from an uppermost electrode layer to said substrate;   (f) depositing a first sacrifice layer around said at least one second opening with a first incident angle;   (g) depositing a second sacrifice layer around said at least one first opening with a second incident angle less than said first incident angle;   (h) forming an emitter electrode on said substrate with said second sacrifice layer being used as a mask.   
     
     
       23. The method as set forth in claim 22, wherein said second sacrifice layer is formed only on an uppermost electrode layer. 
     
     
       24. The method as set forth in claim 22, wherein said second sacrifice layer is formed by oblique evaporation of source material, said source material being deposited with a first incident angle defined so that obliquely evaporated source material is not interrupted by an opening of an uppermost electrode layer and covers therewith an inner sidewall of an opening formed in said first electrode layer. 
     
     
       25. The method as set forth in claim 22, wherein said first sacrifice layer is formed by oblique evaporation of source material, said source material being deposited with a second incident angle defined so that evaporation of source material is not interrupted by edges of an opening formed in an uppermost layer and source material deposits on an inner sidewall of an opening formed in an electrode layer located below said uppermost layer. 
     
     
       26. The method as set forth in claim 22, wherein the first sacrifice layer has a greater density than a density of said second sacrifice layer. 
     
     
       27. The method as set forth in claim 22, wherein said first sacrifice layer is formed by oblique evaporation of source material, said source material being deposited with a second incident angle defined so that said second sacrifice layer covers said second sacrifice layer therewith. 
     
     
       28. The method as set forth in claim 22, wherein said first and second sacrifices layers are formed with different incident angles in oblique evaporation of source material. 
     
     
       29. The method as set forth in claim 22, wherein said first and second sacrifices layers are formed with incident angles for oblique evaporation of source material being continuously varied. 
     
     
       30. The method as set forth in claim 29, wherein said incident angle is increasing from a first incident angle for forming said second sacrifice layer to a second incident angle for forming said first sacrifice layer. 
     
     
       31. The method as set forth in claim 29, wherein said incident angle is decreasing from a first incident angle for forming said second sacrifice layer to a second incident angle for forming said first sacrifice layer. 
     
     
       32. The method as set forth in claim 29, wherein said incident angle is varied reciprocatingly between first and second predetermined angles. 
     
     
       33. The method as set forth in claim 22, wherein said first and second sacrifices layers are formed with incident angles in oblique evaporation of source material being varied in stages. 
     
     
       34. The method as set forth in claim 22, wherein said first sacrifice layer has a portion formed by oblique evaporation of source material with an incident angle of 70 degrees or greater with respect to an axis perpendicular to said substrate. 
     
     
       35. A method of fabricating a field emission cold cathode, comprising the steps, in sequence, of: (a) forming a first insulating layer on a substrate and further forming a second insulating layer on said first insulating layer;   (b) forming an electrode layer on said second insulating layer;   (c) forming a cavity through said electrode layer and said first and second insulating layers so that said second insulating layer projects inwardly of said cavity beyond said first insulating layer and said electrode layer;   (d) forming a first sacrifice layer covering said electrode layer and a projecting portion of said second insulating layer therewith by depositing sacrifice layer material at a first angle;   (e) forming a second sacrifice layer only above said electrode layer by depositing sacrifice layer material at a second angle; and   (f) forming an emitter electrode on said substrate with said second sacrifice layer acting as a mask.   
     
     
       36. A method of forming an emitter on a substrate, comprising the steps of: (a) depositing a first sacrifice layer around a second opening formed in a second electrode layer with a first incident angle, a first insulating layer, a first electrode layer, a second insulating layer, and said second electrode layer being formed on said substrate in this order;     (b) depositing a second sacrifice layer around a first opening formed in said first electrode layer, with a second incident angle less than said first incident angle, and   (c) forming an emitter electrode on said substrate with said second sacrifice layer being used as a mask.   
     
     
       37. A method of forming an emitter on a substrate, comprising the steps of: (a) forming a first sacrifice layer covering both an electrode layer formed above a substrate with an insulating layer being sandwiched therebetween, and a projecting portion of said insulating layer therewith by depositing sacrifice layer material at a first angle;   (b) forming a second sacrifice layer only above said electrode layer by depositing sacrifice layer material at a second angle; and   (c) forming an emitter electrode on said substrate with said second sacrifice layer being used as a mask.   
     
     
       38. The method as set forth in claim 1, wherein said step (g) includes the steps of: (g1) depositing emitter electrode material on said first sacrifice layer to thereby form said emitter electrode with said opening being used as a mask; and   (g2) etching said first sacrifice layer in selected areas to thereby lift-off unnecessary portions of said emitter electrode material.